Burnishing devices and methods



Jan. 22, 1957 D. L. SCHUBERT BURNISHING DEVICES AND METHODS 2 Sheets-Sheet 1 Filed Aug. 25. 195

5 r .wamm H 15 A 5 m BY WW4 W Jan. 22, 1957 0. SCHUBERT 2,778,394

BURNISHING DEVICES AND METHODS Filed Aug. 23, 1952 2 Sheets-Sheet 2 'IIIII 1-,

INVENTOR. DAZE z. Sam/Beer Wham ATTOE/VE'YS BURNISHING DEVICES ANDrMETHODS- Dale L. Schubert, Tacoma, Wash.

Application August 23, 1952, SeriahNo. 305,961-

3 Claims. (Cl. 144-4509).

This invention is concerned with a process of finishing the edge of'dense fiberboard by burnishing it and with variousdevices which may be utilizedto accomplish this result.

Dense fiberboard, having a density approaching or exceeding l, frequently called hardboard, has at least one of itsfaces, and sometimes both, of. very smooth, hard, and frequently polished character, whereas the central portion of the boards thickness usually is comparatively soft. When the edge of such hardboard is trimmed in'thefinal'stages of its manufacture to provide a straight and clean edge, the lack of uniformity in density over the thickness of the sheetbecomes apparent. To one notfamiliar with the method of manufacture and characteristics of hardboard, such lack of uniformity in texture of the edge-of the hardboardsheet makes it appear thatthe product lacks uniformity and is therefore of inferior quality.

The principal object of the present invention, therefore, is to finish-thetrimmed edge of a hardboard sheet by burnishing it so as to have a hard, smooth, polished texture, and dark color closely comparable to the texture of at least one principal face of'the sheet to provide an attractive and uniform appearance of all exposed parts of the sheet.

A further object is to densify and seal the relatively soft central portion of a hardboard sheet at the edges so as to reduce the possibility of moisture penetrating. into the central portion of the sheet. In thus densifying the edge of a hardboard sheet it is an object, where desired, to bevel the sheet edge slightly to provide an under bevel viewed from the face of the sheet, so as to enable similarly trimmed and finished edges of adjacent sheets to be butted together very tightly.

In the production of such a finished edge an object is to accomplish the trimming and densifying in a single operation, or at least in immediately sequential operations, so as not to increase the fabricating cost of the hardboard by additional handling and processing.

The foregoing objects can be accomplished by relatively inexpensive mechanism which can be. operated economically.

Advantages of representative devices shown in the drawingswhich can be utilized to perform the process of the invention are discussed in. the detailed description which follows.

Figure 1 is a somewhat diagrammatic plan view with parts broken away of mechanism suitable for accomplishing the process of the present invention, and Figure 2 is an edge view of such mechanism having corresponding parts broken away. Figure 3 is an enlarged fragmentary vertical sectional view througha portion of a trimming and burnishing element, and a piece of fiberboard on which it is operating.

Figure 4 is a top perspective view of .a fragmentof hard- .board. showing aparti'ally trimmed. edge. Figure 5 is a sectional. view through edge portions of adjacent hard- United States Patent fied appearance.

Patented Jan. 22, 1957 2 board sheets in abutment, taken in a plane perpendicular to the abutment line.

Figure 6 is a fragmentary face view, and Figure 7 is a transverse sectional view through another type of edge trimming and burnishing element.

Figure 8 is a fragmentary face view, and Figure 9 is a transverse sectional view through a further type of edge trimming and burnishing element.

Figure 10- is a' face view and Figure 11 is a transverse sectional view through still a different type of edge burnishing element.

Figure 12 is a somewhat diagrammatic fragmentary plan view of edge trimming and burnishing mechanism incorporating separate trimming and burnishing elements.

Figure 13 is a fragmentary plan view of trimmingand burnishing mechanism incorporati'ng'separate trimmingand burnishing elements in which an alternative type of burnishing element is utilized.

In the manufacture of dense fiberboard, fiber mat is consolidated in a press. As a result the edge portions of the pressed board are more or less ragged, so that it is necessary to trim them straight as a subsequent step in the manufacturing process. By such pressing operation at least one side of the board is given a smooth, hard, and more or less polished surface by contact with a press platen, and the other surface of the board may be similarly finished by engagement with the opposite press platen, or it. may be, pressed against a screen. In the latter case the screen engaged surface will be harder than thecentral portion of the board, but such surface will not be smooth or polished. In either case the central portion of the. board is somewhat softer than the layers immediately adjacent to the surfaces, and if. aboard is simply cut in a plane transversely of-the board,,the softer central portion is quite apparent by its lighter color and fibrous or strati- The. thicker the board,- of course, the. more pronounced willbe the.contrast betweenthe texture of, the central-portion of the board and. those portionsadjacent to the surfaces.

By the process of this invention theedges of such hardboard panels areburnished by friction, which has the. double eflect of compacting. andthus densifying. the edges so as to seal the relatively soft central portion against the entrance of moisture, and of darkening the color substantially to match that of the board face. In fact it is not. objectionable to. darken the edgeto a color somewhat darker than the surface, but. care should be taken not-to apply too much pressure, nor to apply pressure for too long a period during'the burnishing operation, because of the danger of the edge being given an excessively burned appearance. Particularly to enable the proper effect to be produced on hardboards of different density, it is desirableto enable-the burnishing element-to be, adjusted soas to vary the duration andpressure of. burnishing, and usually it is satisfactory to adjust both. of these factors simultaneously, that is,-when less burnishing action is desired thetime is shortened. and the pressure isdecreased, and to obtaina greater burnishing. effectthe pressure will be increased and the time lengthened.

Since'the edges of a hardboard sheet must be trimmed after the sheet isremoved from the press, it isdesirable in most instances to accomplish the-trimmingand burnishing operations simultaneously and'with the same element. in Figure. l a hardboardsheet, Swhichh as beenipressedis shown carried, by any suitable conveyor 1 to. a; combined trimming. and burnishing element, after which the sheet is received by the discharge conveyor. 2. The combined trimming and burnishing element is a unitary'rotary disk 3 of conventional trim saw materiaL; such as saw ste'ell carried and driven by the shaft 4'. Around the. Periphery of. this disk are saw teeth 5' of the usual sawtype,

would slightly bevel the edge of the fiberboard sheet, as discussed, when the rotative axis is parallel to the sheet, the former would not produce such a bevel if the rotative axes of the burnishing elements shown in Figures 6 to 12 were placed exactly parallel to the sheet and the axis of the burnishing element in Figure 13 were exactly perpendicular to the sheet. Even with these burnishing elements, however, the densified edge of the sheet could be made slightly beveled if the rotative axis of the burnishing element were slightly tilted from the positions mentioned.

1 claim as my invention:

1. The method of finishing the edge of a hardboard sheet which comprises darkening and densifying such sheet edge substantially comparable to a face of such sheet by pressing a rapidly moving hard surface against such edge, the pressure and speed of such hard surface being sufiicient to burn and compact such sheet edge to elfect such darkening and densifying.

2. The method of finishing the edge of a hardboard sheet which comprises darkening and densifying such sheet edge substantially comparable to a face of such sheet, and simultaneously beveling such sheet edge, by pressing a rapidly rotating hard surface against such edge, the pressure and speed of such hard surface being sufficient to burn and compact such sheet edge to effect such darkening and densifying, and the application of the hard surface being at such an angle to such edge as simultaneously to effect such beveling thereof,

3. A burnishing machine for burnishing hardboard, comprising means operable to support a piece of hardboard disposed substantially in a plane, a burnishing roller having a burnishing periphery rotatable about an axis extending transversely of such plane and engageable with such piece of hardboard, means operable to drive said burnishing roller rotatively at a considerable speed, means operable to effect relative movement of said burnishing roller and such piece of hardboard along such piece of hardboard, and means operable to support said burnishing roller in position pressing against the hardboard piece while rotating and for movement toward and away from such hardboard piece to alter the degree of pressure of said burnishing roller thereagainst.

References Cited in the file of this patent UNITED STATES PATENTS 231,259 Beehler Aug. 17, 1880 243,292 Naylor June 21, 1881 357,028 Plumb Feb. 1, 1887 783,946 Gregory Feb. 28, 1905 975,886 Murdoch Nov. 15, 1910 1,139,817 Smith May 18, 1915 1,269,653 Smith June 18, 1918 1,395,408 Gale Nov. 1, 1921 2,055,401 Carlson Sept. 22, 1936 

